A device for mutually independent control of regulating devices for controlling fluid flow between a hydrocarbon reservoir and a well which extends from a starting area to the hydrocarbon reservoir, wherein the regulating devices are provided in the well in the hydrocarbon reservoir, where each regulating device comprises a flow controller with a regulating element which is movable between regulating positions for the fluid flow and is connected to an actuating element of a hydraulic actuator, the hydraulic actuator is provided with two hydraulic ports, the actuating element is movable between regulating positions upon a minimum pressure differential between the ports, the differential pressure being provided by hydraulic pipes which extend from the well""s starting area to the hydrocarbon reservoir.
In recovery of hydrocarbons from hydrocarbon reservoirs wells are drilled from a starting area, which may be the seabed or the surface of the earth, down to the reservoir. The wells are lined with casings to prevent the well from collapsing. The casing is perforated in the reservoir area, thus enabling hydrocarbons to flow into the well. Inside the casing a tubing is placed for conveying the hydrocarbon flow to the starting area.
The hydrocarbon reservoirs are located in isolated pockets, which may have a large horizontal area. In the case of such reservoirs the well is drilled vertically down from the surface, whereupon the well is directed horizontally into the reservoir.
The flow of hydrocarbons inside the casing causes the pressure to become higher towards the end of the well. This pressure differential is undesirable, since it can result in the penetration of water and gas into areas with low pressure, which may give rise to flow problems and reduced production from the well.
In order to control the inflow into the well along the length of the well, and to enable the well to be closed off in some areas, sliding or rotation sleeves are employed with flow openings which can be closed by a regulating element which is pushed in the well""s longitudinal direction or rotated about the well""s longitudinal axis.
The sleeves form an integral part of the casing/tubing. They are moved by electric or hydraulic motors, and are operated from the well""s starting area by means of electric cables and/or coil tubing with hydrostatic pressure. The sleeves have to be capable of being controlled both towards an open and closed position, and therefore, when using direct hydraulic control, there must be two coil tubes for each sleeve. The number of sleeves can be large, 10 or more, and direct hydraulic control of each sleeve would therefore entail a large number of coil tubes. Thus the normal procedure is to use an electrohydraulic system where the energy for moving the sleeves"" regulating elements is supplied hydraulically, and the control of the hydraulics is performed by electromechanical valves.
The well may have a depth of 2000 m, and a horizontal length of 3000 m, with the result that the length of the transfer cables and the coil tubes is formidable. On account of both the installation costs and operational problems, therefore, there is a desire to restrict the number of cables and coil tubes.
The pressure down in the well may be 200 to 300 bar, while the temperature may be between 90 and 180xc2x0 C. In this environment regulating devices, and particularly electromechanical components, often become defective after short-term use. The economic consequences of not being able to control the inflow into the well are enormous, and consequently there is a desire to find devices for controlling the flow of hydrocarbons which are simpler and more reliable than the present devices, and it is particularly desirable to avoid electromechanical components in the reservoir area.
When water or gas are injected into a hydrocarbon reservoir, the water or gas in some places might flow directly to a production well, and consequently in the case of injection wells it is also desirable to be able to close or control the flow from the well to the reservoir in specific areas.
U.S. Pat. No. 4,945,995 describes a method and a device for mutually independent, hydraulic control of at least two devices, including flow regulating devices provided in production zones in a well. An object of the method and the device is to reduce the number of hydraulic interconnecting pipes required for the control. This is achieved with a combined electro-hydraulic solution.
WO-98/09055 describes a method and device for selective control of devices disposed down in a well. The control comprises electrical and hydraulic signal connections.
The object of the invention is to provide a device and a method for mutually independent control of regulating devices for controlling fluid flow between a hydrocarbon reservoir and a well which extends from a starting area to the hydrocarbon reservoir, which device and method will be simpler than known devices and methods, and where the components which are employed in the reservoir area will be robust and reliable. A further object is that the number of coil tubes and/or cables will be less than in the case of known devices and methods. Further objects will be apparent from the special part of the description. The objects are achieved according to the invention with a device and a method of the type mentioned in the introduction which are characterized by the features which are stated in the claims.
In the invention both energy and control signals are transferred to the regulating devices only by means of hydraulic pipes. Electric cables and electromechanical components are avoided in their entirety, thereby obtaining a simpler and more robust and reliable control of the fluid flow. Compared to the number of coil tubes/cables which are employed in the prior art, with the invention fewer hydraulic pipes can be employed for independent control of the same number of regulating devices, thereby achieving a simplification of the control. This will be further elucidated in the special part of the description.